FIG. 16 illustrates an example of conventional LED module (see Patent Document 1, for example). The LED module X illustrated in the figure includes a rectangular module substrate 91, on which three LED chips 94R, 94G, 94B are mounted. The module substrate 91 is formed with a plurality of electrodes 92R, 92G, 92B, 93R, 93G, 93B. The LED chips 94R, 94G and 94B are bonded to the electrodes 92R, 92G and 92B, respectively. The electrodes 93R, 93G and 93B are electrically connected to the LED chips 94R, 94G and 94B via wires 95R, 95G and 95B, respectively. The three LED chips 94R, 94G, 94B are covered by a light-transmitting sealing resin 96. The electrodes 92R, 92G, 92B, 93R, 93G, 93B include portions covering the side surfaces and reverse surface of the module substrate 91. These portions are utilized for mounting of the LED module X. The LED chips 94R, 94G and 94B emit red light, green light and blue light, respectively. By mixing the light from the LED chips 94R, 94G and 94B, the LED module X emits white light. By arranging a plurality of LED modules X in a matrix, an LED dot matrix display for use in an electronic message display is obtained.
There is an increasing demand for size reduction of an LED module X. Further, to properly mix the light of different colors, it is desirable that the LED chips 94R, 94G, 94B are arranged as close to each other as possible. However, the LED module X requires a space for arranging the wires 95R, 95G, 95B and a space for arranging the portions of the electrodes 93R, 93G, 93B to which the wires 95R, 95G, 95B are to be bonded, in addition to a space for arranging the LED chips 94R, 94G, 94B. These parts or portions need to be arranged without mutual contact or short-circuiting. Thus, it is not easy to arrange the LED chips 94R, 94G, 94B close to each other and make the LED module X compact.
Further, in recent years, LED dot matrix displays are required to have high resolution. However, when LED modules X are arranged at a high density, the module substrates 91 occupy a large proportion of the display region of the LED dot matrix display. Generally, the module substrates 91, which are made of glass fiber-reinforced epoxy resin, are milk white. Thus, even when all the LED modules X are in the OFF state, the display region of the dot matrix display appears white, which leads to a poor contrast relative to the ON state.
Patent Document 1: JP-A-2003-17753